TY - JOUR
T1 - Ionomer-free electrocatalyst using acid-grafted carbon black as a proton-conductive support
AU - Yoshihara, Ryo
AU - Wu, Dan
AU - Phua, Yin Kan
AU - Nagashima, Akiyo
AU - Choi, Euiji
AU - Jayawickrama, Samindi Madhubha
AU - Ishikawa, Shota
AU - Liu, Xuanchen
AU - Inoue, Gen
AU - Fujigaya, Tsuyohiko
N1 - Funding Information:
We acknowledge Prof. Akari Hayashi for assistance with Pt deposition and useful discussions. The FIB-SEM measurements were conducted at The Ultramicroscopy Research Center, Kyushu University. This research was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan [grant no. 205295 ], under the Nanotechnology Platform Project of MEXT , Japan; KAKENHI [grant no. JP18H01816]; the Bilateral Program [grant no. AJ190078] of the Japan Society for the Promotion of Science (JSPS); the CREST program [grant no. AJ199002 ] of the Japan Science and Technology Agency (JST); the TEPCO Foundation; and the Fukuoka Financial Group Foundation.
Funding Information:
As the grafting acid, sulfonated aryl diazonium was chosen since their radical addition process proceeds under mild conditions (Fig. 1a, see also Supporting Information) [51]. Fig. 1b shows thermogravimetric analysis (TGA) curves of CB after diazonium grafting (SCB) measured under N2 flow. The final weight loss from SCB was larger than that from CB by ∼12 wt%. The weight loss under N2 conditions is often used to estimate the amount of grafted functional groups, with the observed decrease taken as the grafting amount [52]. The TGA curves measured under air flow (Fig. 1c) exhibit one-step thermal oxidation processes starting from 550 to 650 °C for SCB and CB, respectively. The decrease in the degradation onset temperature after grafting indicated that this process introduced sp3 defects onto the sp2 graphitic surface [53]. The X-ray photoelectron spectroscopy (XPS) survey scan of SCB exhibited new S 2p and S 2s peaks at ∼168 and ∼232 eV, respectively, for SCB, whereas no N 1s peaks were detected (Fig. 1d, for the narrow-scan spectra in the S 2p region, see Fig. S1). The zeta potential of SCB was −46.1 mV, whereas that of CB was −8.5 mV (Fig. 1a). SCB also showed excellent dispersion stability, likely due to the strong negative charge on the SCB surface, whereas CB precipitated in aqueous media (inset, Fig. 1b). The above results confirm the successful grafting of benzenesulfonic acid on CB to give SCB.We acknowledge Prof. Akari Hayashi for assistance with Pt deposition and useful discussions. The FIB-SEM measurements were conducted at The Ultramicroscopy Research Center, Kyushu University. This research was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan [grant no. 205295], under the Nanotechnology Platform Project of MEXT, Japan; KAKENHI [grant no. JP18H01816]; the Bilateral Program [grant no. AJ190078] of the Japan Society for the Promotion of Science (JSPS); the CREST program [grant no. AJ199002] of the Japan Science and Technology Agency (JST); the TEPCO Foundation; and the Fukuoka Financial Group Foundation.
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/5/1
Y1 - 2022/5/1
N2 - In the developments of the polymer membrane electrolyte fuel cells (PEMFCs), strategic design of their catalysts layer is a key to improve the performance and durability. Especially, interfacial structure of the electrocatalysts constructed by carbon support, platinum (Pt)-based nanoparticles and polymer electrolyte so called ionomer dominates the performance. It is known that the surface coverage of the ionomers onto the carbon-supported Pt nanoparticles generates overpotentials in the catalyst layer. To avoid this, an ionomer-free electrocatalyst is developed by functionalized surface of carbon supports, in which the support is covalently grafted to benzenesulfonic acid to facilitate the proton conduction on the carbon surface and Pt nanoparticles are attached to the acid-grafted carbon support. In single-cell measurements, although the ionomer-free electrocatalyst exhibits larger proton resistance than a conventional ionomer-based electrocatalyst, higher activity at low (<0.01 A cm−2) and high (>1.7 A cm−2) current densities were achieved owing to increased oxygen reduction reaction activity and decreased oxygen diffusion resistance, respectively. Elimination of the ionomer reduces both the interfacial overpotential as well as diffusion overpotential of the oxygen.
AB - In the developments of the polymer membrane electrolyte fuel cells (PEMFCs), strategic design of their catalysts layer is a key to improve the performance and durability. Especially, interfacial structure of the electrocatalysts constructed by carbon support, platinum (Pt)-based nanoparticles and polymer electrolyte so called ionomer dominates the performance. It is known that the surface coverage of the ionomers onto the carbon-supported Pt nanoparticles generates overpotentials in the catalyst layer. To avoid this, an ionomer-free electrocatalyst is developed by functionalized surface of carbon supports, in which the support is covalently grafted to benzenesulfonic acid to facilitate the proton conduction on the carbon surface and Pt nanoparticles are attached to the acid-grafted carbon support. In single-cell measurements, although the ionomer-free electrocatalyst exhibits larger proton resistance than a conventional ionomer-based electrocatalyst, higher activity at low (<0.01 A cm−2) and high (>1.7 A cm−2) current densities were achieved owing to increased oxygen reduction reaction activity and decreased oxygen diffusion resistance, respectively. Elimination of the ionomer reduces both the interfacial overpotential as well as diffusion overpotential of the oxygen.
UR - http://www.scopus.com/inward/record.url?scp=85126030583&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85126030583&partnerID=8YFLogxK
U2 - 10.1016/j.jpowsour.2022.231192
DO - 10.1016/j.jpowsour.2022.231192
M3 - Article
AN - SCOPUS:85126030583
VL - 529
JO - Journal of Power Sources
JF - Journal of Power Sources
SN - 0378-7753
M1 - 231192
ER -
